A resonance oscillator-based mass detector that wirelessly detects a change in the resonance frequency of a piezoelectric oscillator without using an electrode to sense material to be detected is known (see Patent Document 1).
This resonance oscillator-based mass detector includes a piezoelectric oscillator, a sample supply means, an electric field supply means and a signal analyzer. The electric field supply means includes an input means for inputting a voltage and a receiving means that receives signals of vibrations of the piezoelectric oscillator.
When an electric field for oscillation is applied, the piezoelectric oscillator vibrates due to piezoelectric effects. The sample supply means supplies sample matter onto the surface of the piezoelectric oscillator. The input means of the electric field supply means inputs a voltage to apply an electric field for oscillation to the piezoelectric oscillator. The receiving means of the electric field supply means receives signals of vibrations of the piezoelectric oscillator. Based on the vibrations of the piezoelectric oscillator whose signals have been receive by the receiving means, the signal analyzer detects a change in the resonance frequency caused by material to he detected adhering to the piezoelectric oscillator in order to detect the material to be detected.